Educational projector having movable shutters

ABSTRACT

A projector in which a picture including a plurality of problems and answers is projected on a screen, but the answers are concealed from a viewer, the result of the choice being electrically detected at the same time as operating to reveal the answers.

[451 Oct. 31, 1972 United States Patent Yamamoto [56] References CitedUNITED STATES PATENTS Kozo Yamamoto, l-lirakata, Japan MatsushitaElectric Industrial Co., Ltd., Osaka, Japan Oct. 9, 1970 R23,030 8/1948l-lolt E X 2,783,454 2/1957 North....................35/9 A UX [73]Assignee:

[22] Filed:

Primary Examiner--Wm. H. Grieb [21] Appl. No.: 79,565

Attorney--Stevens, Davis, Miller & Mosher [30] Foreign ApplicationPriority Data ABSTRACT Oct 11 1969 A projector in which a pictureincluding a plurality of problems and answers is pro ected on a screen,but the Japan ......................44/81421 answers are concealed froma viewer, the result of the choice being electrically detected at thesame time as c I-------------|---||--u-.a.--------|-|-- t' t 58 Field ofSearch ..........35/9 R, 9 A, 9 B, 9 E, 9 F, pera mg 6 answers 35/48 R 4Claims, 5 Drawing Figures PATENTED our 3 1 I972 SHEET 1 BF 3 PATENTED nm3 1 I972 SHEEI 3 0F 3 FIG.5

EDUCATIONAL PROJECTOR HAVING MOVABLE SHUTTERS This invention relates toa projector and more particularly a projector to be combined with anoperating device such as a teaching machine.

In a conventional projector to be combined with the multiple choice typeteaching machine, previously prepared answers or instructions for everychoice, are concealed by a shutter from a learner before he choosesanyone. In this kind of projector, however, the result of his choicecannot be symbolized to be recorded. As a result, it is possible for thelearner to advance to the next step regardless of the instructions, eventhough his choice is wrong. Subsequently, there appeared an idea thatthe learners operation 89 for any choice was interlocked with a switchmechanism for opening the shutter. In a more improved projector, theswitch mechanism was further connected with a motoroperated typewriterfor recording the leamers choice. However, these projectors could notresolve a problem in that the leamers next step should be determinedaccording to the answer he chose. For resolving this problem it isnecessary to produce a signal determined by his choice before the answercorresponding to his choice is shown to him.

An object of this invention is to provide a projector system in which apicture including a plurality of problems and answers is projected on ascreen but the answers are concealed from a learner, the result of hischoice being electrically detected at the same moment as operating toreveal the answer. I

The above and other objects, features and advantages will be apparentfrom the detailed description in connection with the accompanyingdrawings in which;

FIG. 1 is a perspective view partially broken showing an embodimentaccording to the invention,

FIG. 2 is a sectional view of an essential part of the embodiment,

FIG. 3 is a circuit diagram, 1

FIG. 4 is a perspective view partially broken showing anotherembodiment, and

FIG. 5 is a sectional view of an essential part of the embodiment.

In FIGS. 1 and 2, reference numeral 1 is a casing providing with ascreen 2 on its side. 3a to 3d are a plurality of shutters respectivelyfitted to a plurality of knobs 6a to 6d which are rotatably mounted on avertical shaft 5. The knobs 6a to 6d are partially projected outside ofthe casing through openings 7a to 7d respectively. The shutters 3a to 3dare turned on the vertical shaft 5 by operating the knobs 6a to 6drespectively. 8a to 8d are photoconductive elements made ofphotoconductive material such as cadmium sulfide which are fixed on aninnerside of the casing 1. 9a to 9d are a plurality of switches, eachhaving a push-button 10a to 10d to be pushed by the schutter when it isrotated. 11 are bushings for maintaining appropriate spaces between theknobs.

In FIG. 3, 12a to 12d are resistors connected in series with thephotoconductive elements 8a to 8d respectively, 13a to 13d arecapacitors in parallel with the series resistors 12a to 12d, 14 is acurrent-limiting resistor, 15 a transistor, 16 a base thereof, 17 anemitter, 18 a collector, 19 a counter and 20 a power source.

Next the description will be made of the operation thereof. In FIG. 1, aplurality of problems according to the multiple choice method areprojected on the screen 2, but answers are concealed by the shutters.The learner operates one of the knobs 6a to 6d corresponding to hischoice, whereby a corresponding shutter is turned to open. Answers to beprojected on the screen at the parts which are now concealed by theshutters 3a to 3d are previously arranged in such a way that-an answercorresponding to the correct choice is projected with a bright picture,e.g., black letters on a white ground, and an answer corresponding tothe wrong choice is projected with a dark picture, e.g., white letterson a black ground. Therefore, the correct answer can be discriminatedfrom the wrong answer by measuring the light quantity of the pictures.The difference between the light quantity of the pictures can bedetected by the resistance of the photoconductive elements 8a to 8d, bywhich the correct answer can be discriminated from the wrong answer.

In FIGJl, assume that the pictures are observed in a direction shown byan arrow mark A and the answer to be projected on the screen at the partwhich is now concealed by the shutter 3a corresponds to the correctchoice and the pictures to be projected on the screen at the parts whichare now concealed by the shutters 3b to 3d correspond to the wrongchoice. If the learner chooses a correct answer and operates the knob6a, the shutter 3a is turned towards the direction shown by the arrowmark B, whereby the answer is projected on the screen so as to beobserved by the learner, while the shutter is turned until thepush-button 10a is pushed by it. Then the switch 9a is turned on. Ag'ainreturn to the original state when the shutter 3a is not yet operated.The resistance of the photoconductive element 8a is reduced to a verysmall value, because the bright picture is projected on the shutter 3a.As a result, most of the voltage across the series circuit of thephotoconductive element 8a and the resistor 12a in FIG. 3 is ap plied tothe resistor 12a whereby the capacitor 13a is charged by the voltage.The resistor 12a and capacitor 13a are so selected that the charge ofthe capacitor 13a is for a time interval from opening the shutter toclosing the switch 9a before being discharged through resistor 12a.Incidentally other photoconductive elements and resistors are arrangedin the same manner. When the switch 9a is closed, the voltage across theresistor 12a is supplied to the base 16 of the transistor 15, wherebythe base current thereof is increased, resulting in increasing of acurrent carried from the emitter 17 to the collector 18. As a result, apulse derived from the increased current causes the counter 19 toactuate. This count represents a correct choice and the counter 19stores this count. If the learner chooses a wrong answer and operatesone of the knobs 6b to 6d, one of the shutters 3b to 3d corresponding tothe knob being operated is turned in the same manner, but the pictureprojected on any one of the shutters 3b to 3d is so dark that thephotoconductive element on the operated shutter presents a resistancevalue much higher than the series resistance 12b to 12d. Hence most ofthe line voltage across the series circuit of the photoconductiveelement and the resistor is applied to the photoconductive element. As aresult, the voltage across the resistor 12b to 12d becomes very low and,the voltage applied to the base 16 of the transistor 15 through theswitch 9b to 9d is also low, whereby the current flowing through thecollector is too small to actuate the counter 19.

In FIGS. 4 and 5 showing another embodiment, photoconductive elements 8ato 8d are respectively mounted on angle frames 21a to 21d which arefixed aside the switch 90 to 90! respectively. Concave reflectors 22a to22d are respectively provided on the shutters 3a to 3d. The projectedlight is reflected by the concave reflectors so as to focus on thephotoconductive elements 8a to 8d. I

As aforementioned, if the learner chooses one of the answers andoperates a knob corresponding to his choice, a picture showing answersrelevant to the choice is projected on the screen, whereby the learneris able to know visually whether his choice is correct or wrong, whilethe photoconductive element electrically detects the result of hischoice, from the brightness of the picture. A signal derived from theelectric detection can be used for any purpose.

What is claimed is:

1. A teaching apparatus comprising:

a screen on which a plurality of images may be projected, said imagesrepresenting multiple choice problem and answer sets;

a plurality of shutters movably mounted adjacent said screen;

means for moving said shutters between first positions in which saidshutters are disposed in the light path of images being projected towardsaid screen to block said images from being; projected onto said screenand second positions in which at least one of said shutters ismaintained out of said light path to permit a corresponding image to beprojected onto said screen;

a plurality of photoconductive elements which detect the quantity oflight of the images projected toward said screen;

measuring means connected to said photoconductive elements for measuringthe quantity of light of the image projected onto said screen when saidat least one shutter is in said second position and for generating asignal when the measured quantity of light is above a predeterminedminimum level to indicate the choice of a correct answer; and

counter means connected to said measuring means for recording thesignals generated by said measuring means to indicate the total numberof correct answers chosen.

2. A teaching apparatus as defined in claim 1, wherein saidphotoconductive elements are mounted on said shutters on the sidethereof facing the direction from which said images are projected towardsaid screen.

3. A teaching apparatus as defined in claim 1, further comprising:

a plurality of reflecting means mounted on said shutters on the sidethereof facing the direction from which said images are projected towardsaid screen; and

means mounting said photoconductive elements to detect light fromreflected projected images reflected by said reflecting means.

4. A teaching apparatus as defined in claim 1,

wherein:

saidm urin means com rises:

paraii e l co ibmations o a resistor and capacitor connected in serieswith said photoconductive elements;

a plurality of switch means each having one terminal connected to thejunctions of the series connections of said parallel combinations andsaid photoconductive elements; and

transistor switch means connected to the other terminals of said switchmeans, said transistor switch means being energized when one of saidplurality of switch means is closed and a predetermined voltage of saidtransistor switch means is present at the junction of said seriesconnections to which the closed switch means is connected; and

said counter means is connected to the output of said transistor switchmeans.

1. A teaching apparatus comprising: a screen on which a plurality ofimages may be projected, said images representing multiple choiceproblem and answer sets; a plurality of shutters movably mountedadjacent said screen; means for moving said shutters between firstpositions in which said shutters are disposed in the light path ofimages being projected toward said screen to block said images frombeing projected onto said screen and second positions in which at leastone of said shutters is maintained out of said light path to permit acorresponding image to be projected onto said screen; a plurality ofphotoconductive elements which detect the quantity of light of theimages projected toward said screen; measuring means connected to saidphotoconductive elements for measuring the quantity of light of theimage projected onto said screen when said at least one shutter is insaid second position and for generating a signal when the measuredquantity of light is above a predetermined minimum level to indicate thechoice of a correct answer; and counter means connected to saidmeasuring means for recording the signals generated by said measuringmeans to indicate the total number of correct answers chosen.
 2. Ateaching apparatus as defined in claim 1, wherein said photoconductiveelements are mounted on said shutters on the side thereof facing thedirection from which said images are projected toward said screen.
 3. Ateaching apparatus as defined in claim 1, further comprising: aplurality of reflecting means mounted on said shutters on the sidethereof facing the direction from which said images are projected towardsaid screen; and means mounting said photoconductive elements to detectlight from reflected projected images reflected by said reflectingmeans.
 4. A teaching apparatus as defined in claim 1, wherein: saidmeasuring means comprises: parallel combinations of a resistor andcapacitor connected in series with said photoconductive elements; aplurality of switch means each having one terminal connected to thejunctions of the series connections of said parallel combinations andsaid photoconductive elements; and transistor switch means connected tothe other terminals of said switch means, said transistor switch meansbeing energized when one of said plurality of switch means is closed anda predetermined voltage of said transistor switch means is present atthe junction of said series connections to which the closed switch meansis connected; and said counter means is connected to the output of saidtransistor switch means.